Skip to main content

Beginner's Guide: What Is an Electronic Parking Brake (and How Does It Work)?

What is a car's electronic hand brake?

In the dawn of the automotive age, all brakes were mechanical, using either a cable or system of rods to force a friction surface to rub on a metal surface connected to the wheels. Sometime before WWII, most cars had moved to a hydraulic brake system, or as the old timers call them "juice brakes". This system was better in that it was easier to engineer, and easier to keep in proper adjustment, but it could fail suddenly if one of the hydraulic components started to leak. In the late 1960s the United States Department of Transportation mandated that hydraulic systems would have a redundancy for safety, which they still do.

The parking brake, aka emergency brake, aka handbrake, aka e-brake, was until recently still very much like early mechanical brakes, with a cable connected to a pedal or a hand lever. In the past few years, as rear disc brakes became commonplace, electronic parking brakes have proliferated. Instead of hydraulic pressure clamping the rear disc, or a cable pulling a lever arm which turns a screw ramp, an electric motor turns a threaded piston in the caliper, clamping the disc. One of the reasons for automakers moving to electric parking brakes is the automation it allows - an electric parking brake can be programed to activate automatically when the transmission is placed into park.

push button parking brake

Electric parking brakes do add a complication though when you are doing a brake job - you need to know the secret trick to make the computer unscrew the brake piston. That information can of course be found in your Haynes manual. If you can't make the caliper back out electrically, it is usually possible to wind it back with an inexpensive brake caliper tool. But if you try to force a screw type caliper piston back into the caliper with a C-clamp, as we typically recommend with the front caliper and many rear calipers, you can damage the caliper.

If there is a push-button to activate the parking brake in your vehicle, obviously it is an electronic system. If the rear caliper has an electric motor attached to the back of it, instead of a metal cable, that also indicates an electronic parking brake. Typically, to retract the parking brake you need an app for your phone or tablet and an ODBII Bluetooth adapter to connect your phone with your car. Some cars and trucks make it easier though, with a combination of inputs at the dash that will also retract it. Your Haynes manual has all the details.